Caterina Caiazza '05, a geology and chemistry major, spent her summer studying a suite of basaltic rocks from the Mexican Volcanic Belt to determine whether the basalts were saturated with sulfide before eruption. Sulfide is the main carrier phase for sulfur, and will have an impact on the degree to which magma will degas sulfur, as well as the distribution of a group of elements called the platinum group elements. Caiazza presented her research at the 19th Annual Summer Intern Conference at the Lunar and Planetary Institute in August.
Under the guidance of Johnson Space Center scientists Dr. Kevin Righter and Dr. Everett K. Gibson, she used electron microscopy, the electron microprobe, and an infrared source total sulfur analyzer to study a suite of basalts from the Mexican Volcanic Belt. Using olivine, spinel and sulfide mineral analyses and thermodynamic data, she calculated the amount of sulfur expected to be dissolved in the basalts under conditions of saturation (which is a function of bulk composition, oxygen and sulfur pressure and temperature). She then compared the calculated values to those measured using the sulfur analyzer.
Her results showed that only 6 of the 50 samples she studied were sulfide saturated, and most of the samples had lower sulfur contents than expected for saturation. This result could be due either to sulfur loss during degassing of the basalt before eruption, or due to under saturation in the magma chamber. Comparison to lunar, Martian and other terrestrial samples show that although Martian basalts and mid-ocean ridge basalts are sulfide saturated, the lunar samples are not. The low S contents of the lunar samples could be the result of degassing or a lower S content in the lunar mantle. Further work is anticipated in determining whether there is a correlation between platinum group element concentrations and sulfide saturation or under saturation.
After finishing her degree, she plans to pursue a Ph.D. in geochemistry.
The Lunar & Planetary Institute's Summer Intern Program offers selected students an opportunity to participate actively in lunar and planetary research with professional scientists at LPI and the NASA Johnson Space Center. Since 1975, the program has given undergraduates studying planetary and Earth sciences a chance to work in a real research environment. The experience is intended to help them examine and focus their career goals and to encourage their development as planetary scientists.
The LPI is located near the Johnson Space Center south of Houston, Texas. The Institute's primary purpose is to provide, on NASA's behalf, leadership within the scientific community in interdisciplinary research and education on lunar, planetary and terrestrial programs.